Most vehicles with accessories such as campers, trailers, and the like have separate and independent air systems for the vehicle and the accessory. The air conditioner and heater for the vehicle are generally powered by the vehicle's motor and deliver the heated or cooled air through an air spreader into the cabin of the vehicle. The air conditioner and heater for the accessory are usually not only completely independent from those of the vehicle but also completely independent from each other.
The design and operation of air conditioners and heaters for vehicles alone, such as cars and trucks, have been the subject of considerable effort and investment by truck and car builders. These systems have been developed to a fairly advanced state and work well to heat and cool the air within the cabin of the vehicle. In fact, most of these systems are capable of producing more than enough heated or cooled air to maintain a comfortable air temperature within the cabin of the vehicle. On the other hand, the design and operation of air conditioners and heaters for accessories such as campers, trailers, and the like have seriously lagged behind the technology of the corresponding systems found in the vehicle itself. The systems for the accessories are usually small, portable units that are incapable of maintaining a comfortable air temperature within the accessory. Many heaters for accessories are powered by 12-volt batteries, fuel oil, or fuel gas and are either incapable of producing enough heat for the accessory or incapable of satisfactorily circulating the heated air produced in order to maintain a fairly uniform, comfortable air temperature throughout the accessory. Some gas heaters are fully capable of producing enough heat for a camper or trailer; however, these units present a high fire risk and a high risk of asphyxiating the people within the camper or trailer.
The most widely used heaters for accessories such as campers, trailers, and the like are powered by fuel oil or fuel gas. Other popular heaters for accessories are electric and are powered by a 12-volt battery source. Oil or gas powered heaters produce a rather intense heat in the area immediately adjacent the heater and usually require a fan to distribute the heated air throughout the interior of the accessory. This presents the additional need to supply a power source for the fan as well as the accompanying problems of noise and reduction of the available space within the accessory. Even with a fan to circulate the heated air, the air temperature within the accessory is usually very uneven with some areas being too hot and other areas being too cold. Heaters powered by fuel oil or fuel gas also present grave risks of fire, burns, and asphyxiation if not operated properly. They are also difficult or impossible to regulate with a thermostat and the operator must either get up several times during the night to adjust the settings on the heater or else pick a particular setting and leave it there for the entire night. If the heater is left at one setting for the entire night, the air temperature within the accessory is usually too hot at one point of the night and too cold at another point in the night.
Like gas and oil heaters, electric heaters also present a risk of fire and burns. Further, they generally will not produce enough heat for medium-sized and larger campers and they will drain a 12-volt battery if used over an extended period of time. Electric heaters also have the problem of battery upkeep and failure. Battery failure is often unpredictable as well as being sudden and complete, leaving the operator with no heat source at all. As with fuel oil and fuel gas heaters, electric heaters using fans present the additional need to supply a power source for the fan as well as the accompanying problems of noise and reduction in the available space within the accessory.
Air conditioners for accessories such as campers, trailers, and the like are usually powered by either gas or electricity. Most electrically powered air conditioners require a 110-volt power source. It is usually impractical to provide a generator for such an electric air conditioner in the vehicle-accessory outfit and, as a result, the air conditioner can only be run when a 110-volt source is readily available as in a trailer park. Gas powered air conditioners are usually bulky, difficult to operate, and costly. Their size alone is a major drawback in that it greatly reduces the available space within the camper. If positioned outside the camper, they increase the air drag on the camper as it moves and are prone to theft and exposure to the elements.
The only known arrangement for using the heater and air conditioner of the vehicle to condition the air within the accessory involves the use of an inflated donut. In this arrangement, the back window of the vehicle and the front window of the camper are removed or slid open and an inflatable donut is placed around the windows and between the vehicle and the camper. Conditioned air from the vehicle's cabin then drifts back into the camper. This arrangement has proven to be most unsatisfactory. First, it is almost impossible to achieve an effective seal between the vehicle and the camper using a donut. The donut rarely makes a good seal between the vehicle and camper when the outfit is stationary, let alone when the vehicle-camper outfit moves over the road or ground. As the outfit is driven, the relative movement of the vehicle and camper makes it almost impossible to maintain a good seal with a donut. This relative movement of the vehicle and camper also produces a rubbing force on the donut and quickly wears it away and produces air gaps.
In addition to these problems with the use of a donut arrangement, there is the problem of circulating the air between the vehicle and the camper. The heater-air conditioner system of commercially available vehicles are only designed to circulate air within the cabin of the vehicle. As a result, the use of a donut arrangement ends up making the cabin too hot or too cold to bear while the air temperature within the camper is hardly changed.
No satisfactory air transfer system for using the heater-air conditioner system of a vehicle to directly heat or cool the air in an accessory such as a camper, trailer, and the like is known to be available. U.S. Pat. No. 1,936,062 to Masury issued on Nov. 21, 1933, diverts a portion of the hot exhaust gases from the vehicle's engine through pipes 29 and 30 into a heat exchanger or radiator 26 mounted in the accessory. A fan 31 blows the air in the accessory over this radiator in which the hot exhaust gases are passing. The air within the accessory forms a closed system and the hot exhaust gases never mix with it. Masury also has a separate and independent air cooler mounted within his accessory. U.S. Pat. No. 3,814,314 issued to Morden on June 4, 1974, and U.S. Pat. No. 3,868,060 issued to Mitchell on Feb. 25, 1975 both circulate the hot engine's coolant through lines in a closed system in which a portion of the closed system passes into the interior of the camper where a fan blows air over that portion of the system. In a manner similar to the teachings of Morden and Mitchell, Anderson in U.S. Pat. No. 3,381,316 issued on May 7, 1968 circulates his hot engine's coolant in a closed system in which a portion of the system passes through the shower water in the camper. Hot coolant from the engine of Anderson's vehicle is passed through the closed system consisting of lines 27, 29 and 35. Line 29 is a heat transfer coil that heats the water 33 in the shower system of the camper.
None of the above-cited U.S. Patents discloses an air transfer system for using the heater-air conditioner system of a vehicle to directly heat or cool the air in an accesory such as a camper, trailer, and the like attached to the vehicle.
The ideal air transfer system for a vehicle-accessory outfit would place the air within the accessory in direct fluid communication with the heater-air conditioner system of the vehicle. It would be safe, inexpensive, and easily installable in commercially available vehicle-accessory outfits. Further, the ideal air transfer system for a vehicle-accessory outfit would quickly and efficiently condition and maintain the air within the accessory at a comfortable temperature without increasing or decreasing the temperature within the cabin of the vehicle beyond a comfortable range. The air transfer system of the present invention provides such a system.